


My Demon Deals in Sin

by Fiorea



Category: Shingeki no Kyojin | Attack on Titan
Genre: Alternate Universe - Fantasy, Alternate Universe - Magic, Fantasy, Humor, M/M, Magic, Mythology - Freeform, Smut, Violence, Wizard!Eren, demon!Levi
Language: English
Status: In-Progress
Published: 2016-03-18
Updated: 2016-07-02
Packaged: 2018-05-27 10:37:15
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 3
Words: 8,627
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6281296
Author URL: https://archiveofourown.org/users/Fiorea/pseuds/Fiorea
Summary: <blockquote class="userstuff">
              <p>Eren Yeager, wizard, discovers that in order for him to use demonic magic, he needs to swap spit with a demon. But spit isn’t the only thing that works, and he's not complaining.</p>
            </blockquote>





	1. They're Called Sparkle Rocks

**Chapter 1: They're Called Sparkle Rocks**

A ball of fire exploded on impact, illuminating the dark clearing and its surrounding trees. Retracting his glowing hand, Eren dashed to the center and turned to face the angry mob of shrieking goblins scampering after him with raised axes and spears.

“Oi, why the fuck are you stopping where they can surround you?” Levi asked from above.

Eren scowled up at the demon who was idly flapping large, leathery wings several meters in the air. “To fight them, obviously. Not everyone has wings they can use to conveniently fly away.” He threw his hand high toward the night sky and, with a downward sweep, called upon a hail of fire. The goblins’ shrieks rose in volume as their comrades were shot down by flames, but more rushed out from the forest to replace the fallen. “I presume you’re not going to help?”

“Think of it as practice. Demonic fire magic only.”

The wizard groaned and ruffled his messy brown locks in frustration. “It would be so much faster if I just buried or froze them.” He dodged an axe flung his way and slammed his sneakered foot into a hideous face before the goblin could claw his side and tear his favorite t-shirt. In one fluid motion, Eren unsheathed the wicked short sword harnessed to his back and lopped the head off a larger goblin. Warm blood the color of charcoal splattered across his face and torso, ruining the shirt anyway. Bummer.

From the corner of his left eye, Eren could make out the demon lounging in the air, picking under his nails with a bored expression as if there wasn’t a fierce battle taking place below. “If you’re just going to watch—or not watch I guess,“ the wizard corrected when Levi didn’t spare a glance, “at least give me some light so I can see the little buggers." No response. "…Or not, asshole.”

Eren drew a deep breath, held it in his chest for two seconds to mix with demon magic, and blew out a powerful stream of fire, bulldozing into the horde of half-naked, somewhat-humanoid creatures. He thought it had bought him some time to prepare a larger attack, but he suddenly heard the whistling of an arrow cutting through air and barely ducked in time to avoid getting impaled.

Eren groaned. The fuckers brought archers! He was fully surrounded now, slashing and hacking his snarling attackers expertly, but for every goblin he cut down, two more replaced it.

“Jeez, all I did was accidentally blow up one of their caves.” Eren channeled fire into his sword and carved into a body. “They have hundreds of them! There’s no reason to freak out.”

“Idiot, you blew up their storage bunker and liquefied half of their gold,” Levi pointed out.

“Don’t they know-” Eren grumbled and dodged an arrow, “not to keep all their eggs in one basket?” More arrows fell upon him, slashing his right arm and left thigh. Aww, he liked those jeans too.

The wizard began chanting under his breath as he stabbed through two goblin chests with one forceful thrust of the sword and then used the mass like a club to bash one more into the ground.

As he kicked off the two dead goblins, Eren flung his hand in front of him, open-palmed, and shouted the last syllable of the incantation. A pulse of energy exploded outwards, shoving the goblins back several steps. A few even toppled over as their legs were swept out from under them.

A moment later, the second stage of the spell initiated to materialize a circular wall of fire around Eren, twisting and howling angrily like a tornado. The twister expanded in diameter as he pumped more magic into the attack, tossing goblins into the air and torching them with ease.

“Watch it, brat! You almost singed my wings,” Levi snapped, beating his wings to cool them down. “It’s not supposed to look like the Leaning Tower of Pisa.”

“You only taught me this move yesterday!” Eren pouted and defended in a strained voice. “I can’t help that it wants to be slanted. Demon magic isn’t exactly friendly, you know.”

The pungent stench of burnt flesh filled the air as the twister died down to small flames scattered here and there. The goblins were now hesitating at the edge of the clearing, chittering amongst themselves in hushed tones and not so enthusiastic now that dozens of their comrades had been wiped out in less than 15 minutes.

Taking advantage of the lull in attacks, Eren passed his sword to his left hand and formed the shape of a gun with his right, the thumb pointing up and the index and middle fingers extending forward. He took aim and shot 6 compressed bursts of fire magic from the tips of his two fingers in quick succession, straight at the goblin archers crouched in the trees. Six thuds of bodies hitting the hard ground were heard clearly by all as the goblins fell silent.

“Guys, I’m really, really sorry about the gold,” Eren called out. “…And your friends,” he added as an afterthought, raising his hands in a placating manner. Realizing that waving a bloody sword around wasn’t helping his plea for peace, he sheathed it immediately and tried to lighten up his grimace.

Receiving no response, Eren groaned and repeated his words in broken Goblinese. He flushed in embarrassment when Levi snickered from somewhere above.

“Shut it!” Eren hissed under his breath, “I know my accent is shit.” This was exactly the reason he avoided using the language.

Across the clearing, the chittering resumed, growing angrier and louder by the second. Shit shit shit shit, Eren thought frantically as the voices became shrieks. He only had enough demon mana for one more mid-scale attack, but Levi would not be pleased if he disobeyed and drew on his natural magic. He would rather fist fight with a mob of angry goblins than incur the demon’s ire.

“Halt! What if me gives, um-,” Eren cut off his grammatically atrocious goblin-speak to open and rifle through his messenger bag. The bag was spelled to hold much more than its outer appearance, but because it could fit so much, he tended to accumulate junk. A lot of junk. Good thing Levi never looked inside.

“Aha! Me gives you, uh…sparkle rocks of big dragon.”

More snickers, louder this time, could be heard from the demon. Eren gritted his teeth in irritation. So what if his vocabulary was severely limited? It was getting the message across just fine!

The wizard hoisted out a heavy sack twice the size of his messenger bag—thank merlin for magic—and removed a large sapphire and gold necklace from inside. “Me steals it from dragon of Mount Nedley. Dragon very mad. Me gives to you, so now dragon sparkle rocks is belongs to you,” Eren explained painstakingly, blundering through the foreign language like a puppy tripping over its first steps.

He could see the goblins craning their necks curiously, trying to get a better look at the jewel without moving closer. Eren tossed it to them and smiled encouragingly.

They immediately crowded around the piece of jewelry, poking at it cautiously with the tip of a spear. Eren lit a small ball of fire over his palm and floated it over to give them light. The goblins flinched in unison at the sight of fire but calmed after seeing that the unmoving flame was not an attack.

It was common knowledge among supernaturals that goblins loathed dragons for having better treasure collections. Goblins were extremely competitive when it came to loot, and losing out to dragons for several millennia was a major stain in their long history.

Under the careful watch of over a dozen pairs of beady eyes, the largest goblin, probably the commander, gingerly lifted the necklace to his face, turning it over and over in his hand to inspect every surface for authenticity. Then he positioned it beneath his hooked nose and took a loud whiff. The goblin recoiled in disgust, but a moment later he thrust the necklace up triumphantly with a loud screech of “dragon!” in their cacophonous language.

The surrounding goblins shrieked their approval, hopping up and down and stomping their feet. A few were even banging their heads on the ground, and Eren wondered if maybe it was brain damage that kept them stupid.

In a graceless scuttle, the leader boldly closed the distance as Eren backed away from the sack of jewels. The goblin yanked the sack open to peer at the mound of treasure collected within. With a disturbingly knotted arm, he rummaged through the precious rocks, stopping every once in a while to examine them.

Making a guttural, satisfied noise in the back of his throat, the goblin gripped the hefty sack firmly and dragged it back to the rest of the goblins that had begun migrating back into the trees. After one last critical look at Eren, the goblins melted into the shadows, leaving him and Levi alone in the clearing.

Eren breathed out a sigh of relief, so very thankful that goblins cared more about pissing off dragons than being pissed at him.

“About fucking time.” Levi landed silently next to the wizard and vanished his wings. “When did you rob a dragon?” He asked, amusement coloring his voice.

“Around a decade ago on a drunk dare. Jean and Reiner ganged up on me.” Eren grinned. “I held onto it in case I needed to bribe someone.”

They slowly made their way through the thick forest, fighting off branches and avoiding nests of hostile, supernatural creatures. “Why can’t you just fly us out of here?” Eren asked as he tripped over a gnarled tree root. Levi caught him by the arm and righted him.

“Because you weigh as much as a baby cyclops,” the demon replied lazily and shifted to grasp Eren’s hand.

The wizard glowered at Levi’s back. He did not! He was a healthy weight for a young, 137-year-old male, and it was mostly muscle and a fantastic ass. “If you’re going to complain, I’ll just find another de- mmf!”

Eren suddenly found himself shoved against a tree and his mouth plundered by a long, hot tongue. He moaned softly as it split in two at the tip to stroke every crevice, taking extra care to fondle the sensitive roof of his mouth.

Eren’s body arched as Levi ran hot fingers down his side, lower and lower until the calloused hand dipped inside his jeans to knead his ass. Heat pooled between his legs, hardening his cock in anticipation of the mind-blowing pleasure the demon never failed to give. He wanted Levi’s leaking cock to rub against his own so bad, to feel the ridges slide across his sensitive skin. The friction, the heat–

The sensations stopped as abruptly as they started. Eren groaned in disappointment when the demon pulled away with a wicked smirk on his swollen lips.

“Never forget, Eren. You’re mine,” Levi growled, deep and feral. Grinding a palm hard against the bulge in the brunet’s pants, his smirk widened when Eren bucked helplessly. “No one else can touch you. No one else can give you the pleasure I can. _Understood?_ ”

The wizard nodded weakly as hot, demonic magic flooded his system, only partially replenishing what had been used in the battle and leaving him wanting more. More of both the rush of power and Levi’s sweet torture.

The demon pressed a searing kiss full of dark promise to Eren’s lips before grasping his hand again. “Hurry up, let’s go home. Your ass needs punishment for that little comment. ”

Eren shuddered involuntarily. Oh hell, yes please.

**Notes for the Chapter:**

> Does this have potential for a multi-chap fic?


	2. Albino Donkey Shit

**Summary for the Chapter:**

> Jean has the absolute worst ideas.

**Notes for the Chapter:**

> This is now officially a multi-chapter story made up of a mishmash of magic, fantasy, mythology, sci-fi…almost everything fictional you can think of that don’t usually cross over. There will be adventure, silliness, and hopefully some decent smut. Thanks for your feedback and encouragement!

**Chapter 2: Albino Donkey Shit**

It all started two years ago with Jean, a help wanted listing, and a bet.

Everyone knew Jean plus the word “bet” in any context was a disaster in the making, especially when Eren got involved, willingly or not. This time, the brunet’s absentee self-preservation instincts showed up for once, and he was most certainly unwilling, but Jean had somehow cornered him into taking up the challenge.

“I can’t believe you’re blackmailing me,” Eren groused. “This has to be one of your worst ideas, right behind the time we started the crop circle hype in the Human Realm.”

“You can’t deny it was fucking hilarious,” Jean watched his friend smugly and brushed off Eren’s grumbled _“yeah, until they banned us from entry for 15 years.”_

“So are you going to do this, or are you wimping out?”

The two wizards were sitting on Eren’s couch, huddled over his laptop like every other time they planned something stupid (though the brunet had to admit "plan" was a generous term when it came to the two of them). Eren scrolled through the help wanted posting for the third time, thinking perhaps it would be prudent to listen to that niggling voice of reason, which sounded like Armin in a panic.

“Don’t be a pussy. All you have to do is to take a field trip to Hell, sweep some floors, and get a signature. It’ll take at most a week.”

Eren looked at his friend as if he had lost his mind; obviously it wasn’t going to be that easy.

“Yeah, except it’s Levi fucking Ackerman.” He felt genuine fear start to creep up for the first time in years. “Rumored to be the greatest evil since Sauron and won’t hesitate to suck out your beating heart with a vacuum cleaner before booting you to the 7th Circle of Hell for even _thinking_ about touching anything with unwashed hands. I might be suicidal, but not _actually_ suicidal.”

“Psh, Sauron was an idiot to put his powers into cheap jewelry.” Jean waved off, unfazed. “Just focus on the payout. You’d be set for a year, or you could finally buy the albino donkey shit you’ve been eyeing for months. That’s nasty, by the way.”

Eren shot him a glare. “ _Unicorn_ dung has over 50 known healing properties. Think of all the new potions I could create.” He paused, then smiled a little too innocently. “Remember that ointment I made for your STI?” Jean clearly had no desire to remember the consequences of his lapse in sexual protection as his face burned bright red. “It had fairy urine in it.”

Jean’s eyes bugged comically.

“The alkaline smell—that was from the vegetarian diet of male Eastern tree fairies,” Eren lectured matter-of-factly, trying to hold in an unmanly giggle. “Fairy magic naturally infuses with ripe urine in a full bladder, creating the perfect creamy base for healing concoctions when it’s whisked, like yellow whipped cream. It was pretty awkward asking them to drop their pants–”

“Alright! Just shut up about it!” Jean was now looking rather green.

A beat later, Eren’s poker face crumbled, and he broke down laughing. “You- you should have seen your face,” he gasped out, struggling to breathe. “You really thought I would use–”

“I wouldn’t put it past you,” Jean muttered and whacked Eren hard on back of the head, causing him to nearly plant his forehead into the laptop screen. “So are you going to do it or not?” He asked gruffly once the laughing died down and Eren cleared his throat.

“Only if you come too. If I’m going to get my ass kicked by the deadliest demon alive, you’re going down with me.”

“Sorry man, can’t,” Jean apologized without a hint of apology. “I’m 1/16 angel. I can’t get into Hell without applying for entry three months in advance.”

Eren scoffed as he recalled their century of shenanigans and troublemaking. “Bullshit. Absolutely _nothing_ about you is angelic.”

“Want me to pull up my genealogy report? Or you can ask my mom.”

A quick phone call later, Eren sat dumbly with horseface preening next to him. “That shouldn’t even count… You’re one of the biggest douches I know.”

“It’s enough for Border Control to make a fuss,” Jean said, looking a little disappointed.

“Sounds suspiciously like you’ve tried before.”

“I’m surprised you haven’t.”

“It’s a little further down on my bucket list,” Eren admitted.

Jean clapped the brunet on the back with exaggerated cheer. “Well, it’s your lucky day! You get to check it off your list early.”

“I have no desire to die early,” Eren protested, but he was already inching the cursor on the screen toward the ‘Accept Job’ button as his thrill-seeking nature got the better of him. “So, I just need to complete the cleaning job and somehow get Hell’s Strongest to sign your lame ass “Hell hath no fury...” t-shirt—this is the dumbest dare ever. Can’t believe I’m risking my life for a measly signature. If I don’t make it back, tell Mikasa, Armin, and mom that I died valiantly for a noble cause.”

“Stop being dramatic, Yeager. If you don’t make it back, I’ll send Mikasa to fish your corpse from the trenches. I heard he prefers to leave his victims in one piece so blood doesn’t splatter his lair.”

“Oh thank god for that.” Eren’s voice dripped with sarcasm. “I’ll be dead, but at least I get an open-casket funeral.” The cursor hovered over the button, fidgeting in tandem to the nervous twitch in his hand. Squeezing his eyes shut and turning away from the screen, he finally let the finger fall. It felt like the digital button depressed in slow motion, and he could imagine thunder crashing through the sky forebodingly… nevermind, that was just his stomach growling.

Jean let out a whoop and ruffled Eren’s hair. “Since I’m a nice guy, you can have 1% of what I make from auctioning off the shirt.”

“’Nice guy’, my ass,” the brunet muttered and jabbed an elbow into his friend’s ribs. “I’m going to come back as a poltergeist to haunt you and your descendants for eternity.”

Jean wheezed a laugh. “Right, whatever you say. Just don’t peek in on me doing the do with my future smokin’ hot wife,” he said, waggling his eyebrows.

Eren dropped his face into his hands and wondered why they were still friends.

~~~~~~~

A week later, Eren found himself gawking up at the dark castle looming ominously and thinking this would be a very good time to retreat. The building was massive, with black ivy choking the stone walls and tall, steel double doors adding to its menacing aura.

He wondered if all structures in Hell looked this…well, hellish.

Because of his father’s position as Lucifer’s private doctor, Eren had passed through Border Control easily. Jean had gleefully sent him off like he was leaving for a tropical honeymoon rather than to the dominion of evil to play housemaid for Hell’s Evilest. The InterDomain Transporter warped him to the nearest checkpoint, which turned out to be a lonely booth situated on a rocky hill somewhere around the 6th Circle of Hell. It was manned by a half-asleep gargoyle, which took two pokes and finally a shove on the shoulder to snap out of its daze and confirm his arrival.

Hiking up the steep, dirt road, Eren was surprised to see a cloudy sky overhead instead of the jagged ceiling of a cave; he thought Hell was supposed to be underground. (He probably should have read through Hell’s Wikipedia page before venturing into the abyss.) The never-ending blanket of gray and barren scenery made for a dull climb. It took 30 minutes to scale the small mountain made of rust-colored rock, and by the time the wizard reached the top, his neck and back were coated in a layer of sweat.

Eren wiped his forehead with the back of his hand and grimaced at the moisture. His client probably wouldn’t appreciate the cleaner showing up with pit stains and sweat rolling down his face. Before stepping up to the doors, he wiggled a finger and whispered “colligere”. Magic tingled over his skin as the sweat on his body collected into a small floating ball of liquid, which he lowered to the ground to soak into the dirt.

Now rid of the sticky feeling, Eren felt marginally better about what he was about to confront. His gut clenched. He knew no one, except for fucking Jean, would call him a coward for backing out; they would even give him a gold star for good judgment.

Because this was The Levi Ackerman. He was said to be as volatile and violent as he was strong, and his terrifying presence would make even the mightiest cry like a baby. The wizard would be no match for the ancient demon if shit hit the fan.

Eren raised a finger to hesitantly press the doorbell and distracted himself by admiring the latest model of the best magical intercom one could buy embedded in the wall. He studied the modern design and shiny surface at odds with the castle’s archaic stonework until the speaker clicked.

“Name.” A silky voice washed over his senses, and it took him a moment to clear his mind of the rich sound.

“Uh, I’m Eren Yeager. I’m here about the–”

“Get in,” the voice interrupted. Eren frowned.

A standard-sized door made of steel materialized in the section of the wall next to the main doors and swung open on its own. Swallowing thickly, the brunet gripped the strap of his messenger bag and walked through the threshold into a large, dimly lit, open foyer with high ceilings, stone walls, and a stone floor. There were wooden double doors on the left and right walls, and a wide staircase at the other end of the room that split halfway up to the second floor balconies, which wrapped around all three walls.

However, what first caught Eren’s attention were not the grotesque paintings of tortured humans and supernaturals that seemed to move in the dim room or the extravagant, gold chandelier that hung garishly over the center. It was the sharp smell of bleach that permeated the room and stung his eyes. From the strength of the smell, the room must have been practically drenched in it just recently. The clinical cleanliness of it made Eren uncomfortable, and he couldn’t help but nervously turn around to check whether he had trekked in any dirt.

“Brat.”

Eren jumped and almost gave himself whiplash when a voice sounded right behind him. He was met with the sight of a short, attractive man with ear-length, glossy black hair styled in a—was that an undercut? Narrow, calculating eyes were glaring straight into Eren’s teal orbs, and the scrunched nose and frown made him feel like an itty-bitty cockroach about to be exterminated.

“H-hi, I’m Eren. I’m here for the cleaning job,” Eren said, managing to stutter only once. This was a demon. A real, live demon just half an arm’s length away, much too close for comfort. He could see the physical identifying marks on those judging eyes, the thin outline of red around the silver irises and the vertical pupils cutting down the center. It hadn’t really registered back when communication had been via email that he had been exchanging words with a demon, but here and now there was no denying it.

After several awkward seconds of staring, the man turned on his heels and stalked off. Eren looked on in confusion. Had he just been snubbed?

“Oi, are you coming or not?” The man snapped without looking back. Eren hurriedly jogged to catch up. Was this rude shorty Levi Ackerman’s assistant? How was he going to deal with the big boss if his assistant was already this unpleasant? He cursed Jean for the umpteenth time.

Eren followed the man through a door in the corner he hadn’t noticed—or maybe it had also materialized out of nowhere—and through dark corridors with mazelike turns until they were deep in the belly of the castle. He was lost after the fourth turn; there was no easy way of escape now.

The demon stopped abruptly in front of a nondescript door and flicked a light switch. Eren squinted against the brightness and barely managed to avoid walking into him.

“So you own a magic shop and claim to be one of the best cleaners in all realms.” The man looked him up and down skeptically, first at his messy mop of hair, over the dark gray, long-sleeve shirt rolled to the elbows, down his faded jeans, to the scuffed werewolf-hide Converses, and finally back up his lean body to his anxious face. “Your definition of cleaning better not be to blow it up.”

“No, I clean with magic,” Eren said defensively. They had only exchanged a few words and he was already starting to despise this asshole. “So when can I see Mister Ackerman?”

The look he received made him feel like the dumbest creature in history. What was this guy’s problem? Asshole really needed to learn some manners.

Then the expression morphed into a cruel smirk, sending shivers down Eren’s spine.

“You’ll get to see him after the job is done.”

“But what about the contract?”

“We’ll sign the contract after the job is done.”

Eren stared bemusedly. “That’s…not how it works.”

“That’s how it works here,” the demon said, quickly losing patience. “Do you want the fucking job or not?

Eren really wanted to say no, but Jean’s stupid threat crossed his mind. He couldn’t let Mikasa find out about _that_ embarrassing stunt he pulled in Trost. “At least give me some sort of verbal binding agreement that promises I’ll be compensated.”

“After you’re done.”

Eren was starting to lose his temper. “You’re crazy if you think I’m going to risk getting duped, especially with you demons!”

Suddenly he was slammed against the rough, stone bricks, a muscled arm pressed almost painfully into his throat and a hard body pinning his taller one. A hard thigh forced his legs apart, and the hip against his pelvis held him in place.

He felt phantom lips brush his earlobe and warm air ghost over the shell of his ear. “Do you want to repeat that, little boy?” Shit, that voice—the perfect bedroom voice with danger dripping from every syllable—caused his gut to clench, this time not in fear. The demon must have felt his muscles tighten because the weight of the hip shifted to his groin, and the perfect pressure over his cock suddenly _rolled_ , sending a jolt up his spine and his head falling back with a gasp.

He bit his bottom lip to stifle a moan when a hand slipped behind his lower back and ground his cock harder into the demon’s solid body. Eren felt himself hardening and fought the sweet pulses of pleasure—no no no NO. No matter how good it felt, there was no way in Hell he was popping a boner because of this bastard. Gritting his teeth, he willed his useless arms to move and shoved the demon with all the strength he could muster, forcing the shorter man to stumble backwards.

Surprise flitted across the demon’s face before it settled back into impassiveness.

Eren inhaled deeply, then breathed out slowly to will his semi-erection away. He was not turned on by this dickhead. Nope. Sure the guy was attractive for someone half a foot shorter, but the demon’s crappy personality was as off-putting as a firedrake suffering from gas. Besides, he’d been sticking to women lately.

“O-okay, how about I clean one room, and then we discuss the contract after I prove myself capable of meeting your standards?” Eren proposed shakily.

He squirmed under the penetrating stare but refused to back down. Must. Stay. Strong.

“Fine,” the demon finally said curtly as he turned to the door. He spoke a few unintelligible words and swiped his right hand in a wide motion from left to right. The air in front of the door shimmered.

Instantly, a putrid stench smacked Eren in the face.

“Fucking hell! What is that?!” He slapped a hand over his nose and mouth and staggered away from the source of the smell.

“ _That_ is an experiment gone wrong.” The only sign the man showed of being affected was the tightening of skin around his eyes. “There is a…colleague that enjoys conducting questionable experiments. It is not uncommon to achieve…unfavorable results.”

“That’s an understatement,” was what Eren would have muttered if he wasn’t about to pass out from the palpable stink assaulting him. Hastily, he flicked his free hand and sacrificed the last of his breath to choke out several words in Latin. Instantly, the air around him cleared, and he was able to suck in gulps of freshly filtered air.

For the second time, the other man looked surprised. It was Eren’s turn to smirk. However, the darkening of the demon’s expression wiped that smirk off his face. Deciding it was best not to tease an ill-tempered creature of the Underworld, Eren cast the same air filtering spell for him.

Without a word of thanks, Asshole cleared his throat and continued. “Every time an experiment backfires to the degree that even I can’t restore the room, we seal it and she constructs a new lab in a different room.” His tone was tinged with frustration, probably at not only his colleague but himself as well for being incapable of accomplishing the task; he seemed like the type who hated asking for help. “Regrettably, this has happened so many times that we are running out of rooms.”

“But, it’s a massive castle!”

“They’re that shitty,” he said flatly.

“So how many of these labs are there?” Eren asked uneasily.

The demon scowled. “427. There are rooms that have been festering for five centuries.”

427\. Eren’s jaw dropped open. _Four-hundred twenty-seven_. The shorter man reached a clawed finger up to his chin and snapped the mouth shut with a click of teeth. There was a touch of amusement in those harsh eyes as the hand retracted.

“The lab in front us is dated approximately three centuries. Let’s see how you fare.”

Without warning, the door was flung open and Eren, still trying to wrap his mind around 427 rooms, was shoved through, and before he realized what was happening, a gallon of bleach conked the side of his head and the door was slammed shut in his face.

“What are you– Hey, let me out!” He ignored the pain blooming in his temple and banged on the door. The wizard could almost feel the waste and mold threatening to engulf him. No, it wasn’t his imagination; he was actually standing on some kind of ugly flowering bush sprawling densely across a patch of the floor, and the door was definitely green and squishy. “This isn’t funny, Asshole. Are you listening?!” He gathered his magic to ram against the door, but all it did was leave a dent in the wood. The demon had sealed him in!

“You’ll need to repair that as well, brat,” the bored voice carried through the door as Eren threw another blasting spell. “Give a shout once you’re done.”

“I’m shouting now!”

Nothing.

Fuck.

Eren frantically surveyed the room for another exit, but there were only solid walls and a rotting jungle. Large clumps of fuzzy mold the color of puke were thriving on the walls, stringy fungi hung from the ceiling spreading outward from the ceiling lamp, a thick layer of steaming, orange, jelly-like substance was growing from the sink and down to the floor, and strange plants almost as tall as himself and sporting tentacles with stingers were sprouting from overturned equipment.

Again, Eren banged his fist on the door, now charred from his attacks, shouting profanities to no avail. He was locked in with who knows what might have mutated in the last 300 years. The wizard crouched low for a better look under workstations and chairs and whimpered when he spotted fat, mushroom-shaped organisms, the same steaming, orange jelly passing between greenery, and a fat, creepy crawly bug with too many legs scuttling into an open cabinet.

There was an entire fucking ecosystem in here!

Eren would have scrubbed his face with his palms had they not been smeared in mold pulp. This was not how he expected the day to go. He should have expected it to be worse than anything imaginable by the enormous sum of money offered. And he hadn’t even met Levi yet.

The brunet slumped with a resigned groan. Might as well get started. Asshole probably wouldn’t open the door until a reasonable time had passed. Damn the shorty. He was going to show everyone in Hell that when it came to magical cleaning, Eren Yeager was second to none.

And then he was going to shove the gallon of bleach up Jean’s ass.

**Notes for the Chapter:**

> How is it? I was nervous to post chapter 2 since it was already pretty decent as a oneshot. I hope I didn’t disappoint~ ^_^’


	3. Sloppy Chunks for Lunch

**Summary for the Chapter:**

> Eren is enlightened. And it's kinda hilarious.

**Chapter 3: Sloppy Chunks for Lunch**

As a cluster of carnivorous fungi puffed out a cloud of puke-green spores—no doubt poisonous—in his face, Eren was never more thankful for his full-body filtering spell. The organisms had not been pleased when he began zapping them off surfaces with magic, and the vicious-looking ones had taken to spitting yellow and green shit at him. Even the orange jelly had turned an angry red and begun excreting pus, no doubt poisonous as well.

Fortunately, his spell didn’t allow a single disgusting particle to touch his skin. It only allowed oxygen to pass inwards and carbon dioxide to pass outwards. His clothing and messenger bag, however, were a different story. He had belatedly placed a containment charm over them only after the fabric was soaked and coated thoroughly in crap. Sadly, they didn’t look salvageable.

30 minutes after the demon had locked him inside the room, Eren cast the final antibacterial spell over every surface of the room. This must be his greatest cleaning achievement yet. The room practically shined. The silver of surgical tools and metal appliances gleamed under the artificial light of the fungus-free ceiling lamp. And if he removed the filtering spell from his body, he would be able to smell a subtle lemony undertone that was often associated with retail disinfectant sprays.

The only dirty things remaining in the room were the plastic trash bag holding ashes of everything he had burned and himself. And that stupid gallon of bleach.

Humming in satisfaction, Eren turned to the door and bellowed, “hey Asshole! Let me out, I’m done.” Two seconds later, he received a less than welcome response.

“Keep up the disrespect, wizard, and this room will be the only thing you see for the remainder of your worthless life,” the demon hissed, full of dark promise. A jolt of fear (and a bit of indignation) shot through Eren at the sinister tone. It felt like his heart skipped a beat, not in a warm, fuzzy way but more like when you accidentally stepped on a hibernating basilisk’s tail. Why, why, _why_ was he baiting a temperamental demon?

“R-right, sorry…Sir.”

There was a beat of tense silence. Eren sensed the slightest wave of demon magic as the powerful seal was removed from the room, warming his skin for such a fleeting instant that he almost thought he imagined it. The door was pushed open to reveal the black-haired man looking as bored as ever, but his expression morphed into unbridled horror as soon as he caught sight of Eren’s disheveled hair and grimy clothes.

The wizard barely caught the edge of the door with his hands as the demon tried to yank it closed. He threw all his weight into keeping the door from slotting back into place; there was a sinking feeling it would never open again if it closed now, with him stuck inside until he gave in to hunger and really blew up the castle.

“Calm down!” Eren fought against the demon’s formidable strength, bolstering his own muscles with his most powerful enhancement spell. “It’s not as bad as it looks.”

“You look like a piss drunk troll retched sloppy chunks on you,” the demon gritted out as he pulled harder, and the door inched closer to its frame. How was the demon so fucking strong?!

“That’s— _fuck_ —that’s an exaggeration.” Eren’s fingers were starting to slip. “I already got rid of the chunks.” He planted a foot up against the wall for better leverage and strained backwards. “Just hear me out!”

“No, you’re fucking disgusting.” The door was nearly shut.

“I’m under a containment charm so nothing’s dripping. At least look inside. I guarantee there isn’t a single speck of dust,” Eren reasoned desperately. Crap, any more and he would have to let go so his fingers didn’t get pinched off. “And if you find otherwise, I’ll clean all 427 rooms for 3/4 the original price.”

The pressure lightened slightly as the demon considered the offer. “Half.”

Eren made a strangled noise of protest in the back of his throat. “That’s exploitation. If all the rooms are as bad as this one, half won’t even cover the material costs, not to mention labor costs.”

“I’ll provide the bleach and tools. You just need to get on your knees and scrub.”

“Like I said earlier, I clean with _magic_. Scrubbing by hand won’t do anything for this catastrophe, but you know that already.”

There was no reply. Then he heard a “tch” and the pressure on the door vanished, sending Eren flying backwards onto the ground like a rag doll. “Ow, warn a guy next time.” He rubbed his tailbone gingerly. It felt like he had spent the entire day getting caught off guard and thrown all over the place.

When Eren glared up at his host, the demon was no longer paying attention to him, too busy staring in what he assumed was awe. The brunet wasn’t entirely certain because his face had barely changed, but the slightly widened eyes and intense scan of the now spotless room hopefully indicated something positive. The short man took a tentative step inside, and another when nothing jumped out at him, and then he was all over the room inspecting every surface. The wizard mentally patted himself on the back; just getting him to enter the room felt like an accomplishment in itself.

Eren finally felt calm enough to take a mental breather. He had this job in the bag, he was certain of it, and at full price too because there was no way his spells would allow even a particle of dust to settle for approximately three weeks, which was when the protective effect expired and dissipated.

It took him a moment to notice the demon was now glaring down at him appraisingly, head cocked to the right and looking as if he was debating Eren’s existence and value, or lack thereof. The intensity had the brunet questioning himself. Did he miss a spot? No, that wasn’t possible. He hadn’t botched a cleaning job in over 60 years since he perfected his suite of basic cleaning spells, and this room had been bad enough to require two additional advanced spells to repair the 300 years of erosion. Then was it the smell? The man’s filtering spell would have worn off by now. Maybe he preferred lavender…?

“Soooo, what’s the verdict?” Eren asked as he slowly stood, moving carefully as if the demon was a dangerous wild animal. In a way, he was.

“…Not bad,” the man said grudgingly.

Eren held back a retort. “Not bad” was a total understatement. Anyone who saw the before and after shots would be blown away by the results. He bet Asshole was just miffed that Eren succeeded where he had failed.

The demon spun around and swept out of the room. Eren snatched his messenger bag, the trash bag of mutant ashes, and the bleach and followed after him, wanting to just get this whole job started. There were 426 rooms remaining, and even without mental math he knew it would take longer than a week. Maybe it would take long enough for Jean to get that visitor visa to Hell so Eren could drag his fat horse ass by the tail and lock _him_ in one of these nightmarish rooms.

As they walked at a brisk pace through the corridors, the wizard studied the man’s broad back. From what he had seen earlier, the demon wore a blood red button-up shirt under that black, high-collar jacket with overlapping bat wings in two shades of red embroidered prominently on the back. The form-fitting shirt was tucked neatly into black trousers secured around the hips by a black leather belt. He had caught a glimpse of a shoulder harness with a strip of leather crossing the front of the chest for some type of underarm weapons. The badass getup looked roguish yet militaristic, especially with the sturdy combat boots strapped tightly halfway up his calves.

It was, without a doubt, infinitely cooler and more practical than the dumb uniforms in Heaven, which were typically white, fluttery togas; or bulky, protective jackets designed to look like gallant, metal armor from the ancient Greek military, paired with a red kilt and golden, lace-up combat boots. They looked more like cheap Halloween costumes than uniforms.

How embarrassing.

At least Heaven’s independent military institutions had the sense to upgrade to more practical military jackets and pants, although the white fabric stained easily and was excessively embellished with buttons and tassels. He internally rolled his eyes. For a people that boasted sophistication and discipline, it was funny how practicality was lost on them.

The demon stopped at a set of double doors. Unlike the wooden doors they had passed in the corridors, this one was a hefty, steel thing, like a much smaller version of the monstrosity that was the front entrance. It opened smoothly on well-oiled hinges, Eren noted, and they entered a large room with a sharp glance from the shorter man—probably warning him to behave.

“Sit,” he commanded and beckoned to a cozy-looking, gray armchair next to the fireplace with a curl of his clawed finger. The chair lifted an inch off the floor to zoom across the room and park itself in front of a large, ebony, office desk, giving one last wiggle before it settled back to being an inanimate object. Eren gripped the chair firmly just in case it decided to break out into one last jig and lowered himself onto it, while the demon rounded the desk to sit in a leather, high-back, swivel chair that looked like it was taken straight out of an evil villain movie. Surprisingly, it didn’t tower over his short stature as it should have and actually looked kind of cool in an ‘I’ve got the world under my evil thumb’ way.

“…ger. Yeager. Oi, brat–”

Eren jerked out of his staring with a yelp when a paperweight struck the side of his head, right over the bump the gallon of bleach had caused earlier. Slumping over with a pitiful groan, he clutched his head against the jarring pain as his eyes prickled with tears. Eren gave little thought to the contemptuous snort from the demon, too busy blinking away the stars in his vision to care about what the Asshole thought of him at the moment.

“Your performance was satisfactory,” the demon began without preamble. “I am, regrettably, a demon of my word.” With the snap of his fingers, a laptop, monitor, keyboard, and mouse materialized at one end of the smooth, black surface. He opened the lid of the laptop and began typing at lighting speed. In the meantime, Eren glared daggers at him.

Suddenly, the monitor rotated to face him. “Here is your contract. Review and sign at the bottom.”

“Contract…”

The demon rolled his eyes. “You must have been dropped on your head as a baby. You wanted a binding agreement, didn’t you? It’ll be beneficial to me as well, to ensure you don’t skip out before completing all the rooms.”

“Oh, right,” Eren mumbled before scanning through the text document carefully, making mental notes as he read the contract. By the last word, his eyebrows were furrowed and a frown marred his face.

“This looks like a contract a con man would write up,” Eren commented. “It’s vague, and there are bunch of loopholes you can use to take advantage of me.”

The demon only arched a questioning eyebrow. Eren took it as the go ahead to list every flaw.

“So you aren’t completely stupid,” the shorter man said as if he was seeing Eren in a totally new light—now Eren really wanted to punch the little fucker. “Good, I don’t want an imbecile tearing apart my castle.”

They spent the next 20 minutes bickering over the precise wording of the contract, similar to how he and Jean squabbled, except it was different in that, afterwards, he didn’t feel as if his IQ had plummeted like the next stock market crash. There were a few close calls where he thought the demon would fry his ass for making a particularly bold remark, but it was overall rather enjoyable.

“Good enough, brat?” The demon, on the other hand, looked like he was completely done with the conversation…10 minutes ago. There was an ever-present tick mark on his forehead that appeared not long after Eren had pointed out a grammar error, which apparently had been intentional legalese. Yeah whatever, he called bullshit.

“Yup,” Eren answered cheerily. The contract was airtight and bulletproof, at least to his amateur eyes, but he had dealt with enough con men—namely the Connie and Sasha duo—that he could pick out most loopholes without having to squint.

“Then hurry up and sign.”

The wizard tilted his head quizzically. “Doesn’t Mister Ackerman need to review it?”

The flat look he received made him feel dumb all over again.

“On second thought, it might be better to kick your stupid ass out right away. Your stupidity is stinking up the air.”

“What?” Eren squawked. “What’s wrong now?”

The demon pursed his lips. “Look at the bottom of the last page. That’s where you and I will sign.”

He stared at the two names printed under the two signature lines.

“You and me. You and…”

Then it clicked.

Oh.

Shit.

“You- _you’re_ Levi Ackerman?!”

The demon before him—the one that was now rolling his eyes at him—was supposed to be The Levi Ackerman, Hell’s Evilest. “If I didn’t need you for cleaning, I would have fed you to Hanji’s pet kraken by now.”

“How could I have known? You’re supposed to be ancient!”

“Mid-3000’s is not ancient, brat. I’m in my prime,” Levi replied, sounding a little resentful.

“And you’re supposed to be a ruthless killer that eats the hearts of sinners for breakfast in his underground lair decorated with skulls.”

Levi looked incredulous. “What does everyone think I am? Some kind of mindless Neanderthal with disregard for hygiene?!”

“Well, rumor also says your secondary weapon is a handheld vacuum cleaner.”

Levi scoffed. “That’s the lamest thing I’ve ever heard. What other nonsense is there?”

“You’re called Hell’s Strongest–”

The demon interrupted with a snort. “Only because I beat Lucifer at arm wrestling on a regular basis. His abilities still rank above mine.”

“…right, uh…And you’re the greatest evil since Sauron–”

“Tch. Don’t compare me to that piece of shit. No one in his right mind would stick his powers into the wedding ring of his runaway bride, and then rage around Middle-earth in an attempt to prove his masculinity.”

It was Eren’s turn to look incredulous. “I thought he wanted to rule the world.”

“Rule the world?” Levi made a disgusted face. “He couldn’t even manage his own piss at night. Idiot was just throwing a tantrum after the love of his life ditched him for an Elvish prince.”

Eren choked on laughter. “So what you’re saying is, you’re not a senior citizen, you have proper housing, Lucifer arm wrestles, and Sauron had low self-esteem.”

“Basically.”

“And, and you don’t fight with a vacuum.” The wizard laughed harder at imagining the shorter man armed for battle with cleaning supplies.

The unamused glare was back.

Eren hiccupped as he tried to regain his composure. “It’s all on your Wikipedia page. There’s even a distorted photo of you swinging something that looks like a mop.”

A feral growl escaped Levi’s throat, making the hairs on Eren’s skin stand. “Fucking four-eyes! I’ll mutilate their face the next time I see them.”

“Who?” Eren asked through a quickly fading grin.

“The shitstain you’re cleaning up after, who happens to be a Wikipedia administrator.” As an evil gleam entered Levi’s silver eyes, the air around them began to rise in temperature. “I’m certain they’re behind every bit of false information, and for that they are due for a long afternoon of torture.”

This time, the tremble that ran through Eren was one of fear. While bantering, Levi seemed merely like someone with a shitty personality and sick sense of humor, but the magic he was now evoking reminded Eren that Levi was still a powerful demon with rumored violent tendencies, and there was most likely truth to all those exaggerated rumors. “That…sounds like a great plan. How about I sign and get out of your hair so you can find your friend for a nice torture session.”

Eren pointed a glowing finger towards the signature line on the screen and wrote his magical signature in the air, his movements trailed by a streak of light that followed every curve of his name. Simultaneously, the same messy scrawl appeared on the screen. Levi turned the monitor to do the same. At the final sharp stroke, a burning tingle surged through Eren’s body, starting from his signature finger, running up his arm, down one side to his feet, back up and through his other leg and arm, into his head, down into his chest, and finally encircling his heart. A weight, almost unnoticeable, settled in his chest as the heat dissipated.

“Wow, what was that?” Eren asked breathlessly.

“The activation of a demonic contract. It now has a hold on your heart, and as agreed, I am able to track your location by heartbeat until the job is completed to ensure you don’t skimp.”

“I didn’t realize it would be tied around my heart.” Eren pressed a hand over the beating organ, wondering if it would feel any different, but the weight from earlier was no longer there, or perhaps he had already acclimated to it. The thought of being strung on a magical leash was extremely unnerving, but Levi had given his written word to not use it unless under circumstances clearly defined in the contract, and Eren had every intention of finishing the job and getting that damn signature, so unless extenuating circumstances popped up out of nowhere, there should be no need to utilize the tracker…

“What happens if I run out on you?”

“If I’m unable to retrieve you, the contract allows me to eliminate you by ripping out your heart,” Levi explained. Then after a pause, he leaned forward on his elbows as if to impart a secret. “And I’ll eat it for breakfast with my morning cup of tea.”

Eren paled and leaned as far away from the demon as he could within the confines of the armchair. “…Didn’t you say that was a false rumor?”

Levi’s lips stretched into the most malicious smile Eren had ever seen, revealing pointed canines that could easily tear through flesh. “Believe what you will, little wizard. Just know that you can never escape me.”

**Notes for the Chapter:**

> I imagine that out of everything in the digital world, Hanji would choose to be a Wikipedia admin :P


End file.
